Catalyst for production of vinyl-based polymer and process for production of vinyl-based aromatic polymer

ABSTRACT

A catalyst for the production of a vinyl polymer, which comprises: in combination, (A) a transition metal complex of the formula: ##STR1## wherein each of T 1 , T 2 , T 3  and T 4 , independently of each other, is C 1-20  -alkyl or C 6-20  -aryl, M is a Group IV-VI transition metal and Q is C 1-20  -alkoxy, (B) an aluminoxane or ionic compound having a non-coordinating anion and a cation and (C) a Lewis acid. 
     Component (B) can be a combination of an aluminoxane and an ionic compound having a non-coordinating anion and a cation.

TECHNICAL FIELD

The present invention relates to a catalyst for producing a vinyl-basedpolymer such as a polyolefin, and a process for producing a vinyl-basedaromatic polymer by using the same, especially a process for efficientlyproducing a styrenic polymer having a low molecular weight.

BACKGROUND ART

There have heretofore been known the processes for producinghigh-performance styrenic polymers having a high degree of syndiotacticconfiguration in high yield by allowing a reaction product of analuminoxane with a transition metal complex to act on styrene. (Refer toJapanese Patent Application Laid-Open Nos. 187708/1987, 179906/1988,241009/1988, etc.) The catalyst system containing an aluminoxane has theadvantage of high activity, but it is required in the case ofmethylaluminoxane which has a particularly high activity to use a largeamount thereof against a transition metal compound. In particular inorder to obtain a styrenic polymer having a molecular weight of 600,000or less, it is necessary to add a large amount of a Lewis acid to thereaction system or set the temperature at the time of polymerization toa high level. The above-mentioned necessity is responsible for suchproblems as a large amount of ash remaining in the product polymer anddeteriorated catalytic activity.

As a catalyst free from an aluminoxane for producing a styrenic polymerand a process for producing the same without the use of an aluminoxane,there is disclosed in Japanese Patent Application Laid-Open No.249504/1992, a method for polymerizing a styrenic monomer by the use ofa catalyst system which comprises a transition metal compound and anon-coordination ionic compound. However in the case of producing apolymer, a catalyst system not containing an aluminoxane causesdifficulty in controlling the molecular weight of the product polymer ascompared with a catalyst system containing an aluminoxane. Inparticular, in order to obtain a styrenic polymer having aweight-average molecular weight of 600,000 or less, it is stillnecessary to add a large amount of a molecular-weight depressant to thepolymerization system or to set the polymerization reaction temperatureat a high level. Such necessity brings about a decrease in the catalyticefficiency and an increase in the amount of residual ash, therebyincreasing the polymer production cost and deteriorating the physicalproperties of the resulting polymer.

Under such circumstances, it is an object of the present invention toprovide a catalyst for producing a vinyl-based polymer capable ofefficiently producing a vinyl product-addition polymer such aspolystyrene and polyolefin as well as a process for efficientlyproducing in a low production cost, an aromatic polymer having a lowmolecular weight and a high degree of syndiotactic configuration.

DISCLOSURE OF THE INVENTION

As a result of intensive research and investigation accumulated by thepresent inventors for the purpose of attaining the above-mentionedobject, it has been found that the object can be attained by the use ofa polymerization catalyst which comprises in combination, a transitionmetal compound having a tetra-substituted cyclopentadienyl group as aπ-ligand, a specific promoter or an ionic complex and a Lewis acid. Thepresent invention has been accomplished on the basis of the foregoingfinding and information. In addition, the present invention providesmore useful means for solving such problems as catalytic efficiency,thermal stability of the transition metal compound itself, ease ofpurfication, molecular weight of the resultant polymer etc. in the caseof using the above-mentioned transition metal compound having atetra-substituted cyclopentadienyl group as a π-ligand.

Specifically, the present invention provides

(1) a catalyst for the production of vinyl-based polymers whichcomprises in combination, an (A) transition metal compound having atetra-substituted cyclopentadienyl group as a π-ligand, a (B)aluminoxane and/or ionic compound having a non-coordinating anion and acation and a (C) Lewis acid; and

(2) a process for the production of vinyl-based aromatic polymers whichcomprises producing a vinyl-based aromatic polymer by the use of theabove-mentioned catalyst in item (1).

As the catalyst for the production of a vinyl-based polymer according tothe present invention, the combination of the aforesaid components (A),(B) and (C) is used. As the transition metal compound having atetra-substituted cyclopentadienyl group as a π-ligand as the component(A), there are preferably used a transition metal compound having onetetra-substituted cyclopentadienyl group as a π-ligand and also atransition metal compound in which at least one σ-ligand is an alkoxylgroup. The former is preferable from the viewpoints of catalyticactivity and controllability for the molecular weight of the productpolymer, while the latter is preferable from the viewpoint of stability.The compound as the component (A) is represented by the general formula(I)

    RMX.sub.3 L.sub.n                                          (I)

wherein R is a tetra-substituted cyclopentadienyl group; M is atransition metal; X is hydrogen atom, a hydrocarbon group having 1 to 20carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms,an alkoxyl group having 1 to 20 carbon atoms, an aryloxyl group having 6to 20 carbon atoms, a thioalkoxyl group having 1 to 20 carbon atoms, athioaryloxyl group having 6 to 20 carbon atoms, an amino group, an amidegroup, a carboxyl group, an alkylsilyl group or a halogen atom and maybe the same as or different from each other, at least one of which ispreferably a group other than a halogen atom, hydrogen atom andhydrocarbon group; L is a Lewis base; and n is an integer from 0 to 2.

The tetra-substituted cyclopentadienyl group represented by R in theforegoing general formula (I), which may be polycyclic, is acyclopentadienyl group in which four carbon atoms out of five carbonatoms which form the ring are substituted with functional groups otherthan hydrogen atom, and specifically a group represented by the generalformula ##STR2## wherein T¹ to T⁴ may be the same as or different fromeach other, and are each an alkyl group having 1 to 20 carbon atoms, anaryl group having 6 to 20 carbon atoms or an arylalkyl group having 7 to20 carbon atoms. Specific examples of this group include1,2,3,4-tetramethylcyclopentadienyl group,1,2,3,4-tetraethylcyclopentadienyl group,1,2,3,4-tetrapropylcyclopentadienyl group,1,2,3,4-tetrabenzylcyclopentadienyl group and1,2,3,4-tetraphenylcyclopentadienyl group.

The transition metal represented by M in the above-mentioned generalformula (I) is a transition metal belonging to any of the groups 4 to 6of the periodic table or to lanthanides series, and exemplified by Ti,Zr, Hf and V, among which Ti is preferable.

X is a hydrogen atom; a hydrocarbon group having 1 to 20 carbon atoms,specifically exemplified by methyl group, ethyl group, propyl group,butyl group, amyl group, isoamyl group, isobutyl group, octyl group,2-ethylhexyl group, phenyl group and benzyl group; an alkoxyl grouphaving 1 to 20 carbon atoms, specifically exemplified by methoxy group,ethoxy group, propoxy group, butoxy group, amyloxy group, hexyloxy groupand 2-ethylhexyloxy group; an aryloxy group having 6 to 20 carbon atoms,specifically exemplified by phenoxy group; a thioalkoxy group having 1to 20 carbon atoms, specifically exemplified by thiomethoxy group,thioethoxy group, thiopropoxy group and thiobutoxy group; a thioaryloxygroup, specifically exemplified by thiophenoxy group; an amino group; anamide group; a carboxyl group; and a halogen atom, specificallyexemplified by chlorine atom, bromine atom, iodine atom and fluorineatom, and may be the same as or different from each other, at least oneof which is preferably a group other than a halogen atom, hydrogen atomand a hydrocarbon group.

Specific examples of the transition metal compounds that are usable inthe process according to the present invention include(1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium triethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium tripropoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium tributoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium triphenoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium trithiomethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium thiophenoxide,(1,2,3,4-tetramethylcyclopentadienyl)zirconium trimethoxide,(1,2,3,4-tetramethylcyclopentadienyl)hafnium trimethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium trichloride,(1,2,3,4-tetramethylcyclopentadienyl)trimethyltitanium,(1,2,3,4-tetramethylcyclopentadienyl)zirconium trichloride,(1,2,3,4-tetramethylcyclopentadienyl)trimethylzirconium,(1,2,3,4-tetramethylcyclopentadienyl)hafnium trichloride and(1,2,3,4-tetramethylcyclopentadienyl)trimethylhafnium. In addition as ahexadentate ligand, mention is made of(1,2,3,4-tetramethylcyclopentadienyl)titanium monochlorodimethoxide and(1,2,3,4-trimethylcylopentadienyl)titanium dichloromonomethoxide.

As the component (B) of the catalyst according to the present invention,there is employed an aluminoxane and/or an ionic compound having anon-coordinating anion and a cation. The aluminoxane and the ioniccompound function each as a promoter or an activating agent.

Aluminoxane is obtained by bringing any of a variety of organoaluminumcompound into contact with a condensing agent. As the organoaluminumcompound to be used as a starting material, mention is made of anorganoaluminum compounds represented by the general formula:

    AlR.sup.1.sub.3                                            (III)

wherein R¹ is an alkyl group having 1 to 8 carbon atoms, morespecifically, trimethylaluminum, triethylaluminum andtriisobutylaluminum, and trimethylaluminum is most desirable.

On the other hand, a typical example of the condensing agent for saidorganoaluminum compound is water. In addition, any compounds capable ofundergoing a condensation reaction with organoaluminum compoundsincluding alkylaluminum can be used.

As the aluminoxane of the component (B), mention is made of a chainalkylaluminoxane represented by the general formula: ##STR3## wherein nindicates polymerization degree, and a number of 2 to 50; and R²represents an alkyl group having 1 to 8 carbon atoms,

and a cycloalkylaluminoxane having the repeating unit represented by thegeneral formula: ##STR4## and the like. Of these alkylaluminoxanes, thatwherein R² is a methyl group, i.e. methylaluminoxane is particularlydesirable.

In general, the contact product of an organoaluminum compounds such astrialkylaluminum and water contains the above-mentioned chainalkylaluminoxane and cyclic alkylaluminoxane together with unreactedtrialkylaluminum, various mixtures of condensates and further themolecules resulting from association in an intricate manner thereof.Accordingly, the resultant contact product varies widely depending uponthe conditions of contact of trialkylaluminum with water as thecondensation agent.

The reaction of the alkylaluminum compound and water is not specificallylimited in the above case but may be effected according to the publiclyknown methods.

As the ionic compound to be used as the component (B), there arepreferably usable the compounds represented by the general formula (VI)or (VII)

    ( L.sup.1 -H!.sup.g+).sub.h ( M.sup.1 X.sup.1 X.sup.2 --X.sup.n !.sup.(n-m)-)i                                            (VI)

or

    ( L.sup.2 !.sup.g+).sub.h ( M.sup.2 X.sup.1 X.sup.2 --X.sup.n !.sup.(n-m)-)i(VII)

wherein L² is M³, R³ R⁴ M⁴ or R⁵ ₃ C as hereinafter described; L₁ is aLewis base; M¹ and M² are each a metal selected from Groups 5 to 15 ofthe Periodic Table; M³ is a metal selected from Groups 8 to 12 of thePeriodic Table; M⁴ is a metal selected from Groups 8 to 10 of thePeriodic Table; X¹ to X^(n) are each a hydrogen atom, dialkylaminogroup, alkoxy group, aryloxy group, alkyl group having 1 to 20 carbonatoms, aryl group having 6 to 20 carbon atoms, alkylaryl group,arylalkyl group, substituted alkyl group, organometalloid group orhalogen atom; R³ and R⁴ are each a cyclopentadienyl group, substitutedcyclopentadienyl group, indenyl group or fluorenyl group; R⁵ is an alkylgroup or an aryl group and may be the same as or different from eachother; m is the valency of each of M¹ and M², indicating an integer of 1to 7; n is an integer of 2 to 8; g is the ion valency of each of L¹ -H!and L² !, indicating an integer of 1 to 7; h is an integer of 1 or more;and i=h×g/(n-m).

Specific examples of M¹ and M² include B, Al, Si, P, As, Sb, etc.; thoseof M³ include Ag, Cu, etc.; and those of M⁴ include Fe, Co, Ni, etc.Specific examples of X¹ to X^(n) include dialkylamino group such asdimethylamino and diethylamino; alkoxyl group such as methoxyl, ethoxyland n-butoxyl; aryloxyl group such as phenoxyl, 2,6-dimethylphenoxyl andnaphthyloxyl; alkyl group having 1 to 20 carbon atoms such as methyl,ethyl, n-propyl, iso-propyl, n-butyl, n-octyl and 2-ethylhexyl; arylgroup having 6 to 20 carbon atoms, alkylaryl group or arylalkyl groupsuch as phenyl, p-tolyl, benzyl, pentafluorophenyl,3,5-di(trifluoromethyl)phenyl, 4-tert-butylphenyl, 2,6-dimethylphenyl,3,5-dimethylphenyl, 2,4-dimethylphenyl and 1,2-dimethylphenyl; halogensuch as F, Cl, Br and I; and organometalloid such as pentamethylantimonygroup, trimethylsilyl group, trimethylgermyl group, diphenylarsinegroup, dicyclohexylantimony group and diphenylboron group. Specificexamples of substituted cyclopentadienyl group of R³ and R⁴ includemethylcyclopentadienyl, butylcyclopentadienyl andpentamethylcyclopentadienyl.

Among the compounds represented by the general formula (VI) or (VII),specific examples of preferably usable compounds include, as thecompound of general formula (VI), triethylammonium tetraphenylborate,tri(n-butyl)ammonium tetraphenylborate, trimethylammoniumtetraphenylborate, triethylammonium tetra(pentafluorophenyl)borate,tri(n-butyl)ammonium tetra(pentafluorophenyl)borate,N,N-dimethylanilinium tetra(pentafluorophenyl)borate,N,N-diethylanilinum tetra(pentafluorophenyl)borate,N-methyl-N,N-diphenylammonium tetra(pentafluorophenyl)borate,triethylammonium hexafluoroarsenate, etc., and as the compound ofgeneral formula (VII), pyridinium tetra(pentafluorophenyl)borate,pyrrolinium tetra(pentafluorophenyl)borate, ferroceniumtetraphenylborate, dimethylferrocenium tetra(pentafluorophenyl)borate,ferrocenium tetra(pentafluorophenyl)borate, decamethylferroceniumtetra(pentafluorophenyl)borate, acetylferroceniumtetra(pentafluorophenyl)borate, formylferroceniumtetra(pentafluorophenyl)borate, cyanoferroceniumtetra(pentafluorophenyl)borate, silver tetraphenylborate, silvertetra(pentafluorophenyl)borate, trityl tetraphenylborate, trityltetra(pentafluorophenyl)borate, tri(p-methoxyphenyl)carbeniumtetra(pentafluorophenyl)borate, silver hexafluoroarsenate, silverhexafluoroantimonate, silver tetrafluoroborate, etc.

On the other hand, as the Lewis acid to be used as the component (C) ofthe catalyst according to the present invention, there are available avariety of organometallic compounds, boron compounds, etc., theorganometallic compounds being preferably exemplified by organoaluminumcompounds represented by the general formula (VIII):

    R.sup.6.sub.r Al(OR.sup.7).sub.s H.sub.t X.sub.u;

wherein R⁶ and R⁷ each independently represent an alkyl group having 1to 8 carbon atoms, preferably 1 to 4 carbon atoms; X represents ahalogen; r, s, t and u are each a number satisfying the relations 0<r≦3,0≦s<3, 0≦t<3 and 0≦u<3 respectively, and r+s+t+u=3.

The organoaluminum compound represented by the above formula (VIII) canbe exemplified as shown below. Those corresponding to t=u=o arerepresented by the formula: R⁶ _(r) Al(OR⁷)_(3-r), wherein R⁶ and R⁷ areas previously defined and r is preferably a number of 1.5≦r≦3. Thosecorresponding to s=t=0 are represented by the formula: R⁶ _(r) AlX_(3-r)wherein R₆ and X are as previously defined and r is preferably a numberof 0<r<3. Those corresponding to s=u=0 are represented by the formula:R⁶ _(r) AlH_(3-r), wherein R⁶ is as previously defined and r ispreferably a number of 2≦r<3. Those corresponding to t=0 are representedby the formula: R⁶ _(r) Al(OR⁷)_(s) X_(u) wherein R⁶, R⁷ and Y¹ are aspreviously defined and 0<r≦3, 0≦s<3, 0≦u<3 and r+s+u=3.

In the organoaluminum compound represented by the formula (VIII), thecompound wherein t=u=0 and r=3 is selected from, for example,trialkylaluminum such as triethylaluminum and tributylaluminum, orcombination thereof, and those preferred are triethylaluminum,tri-n-butylaluminum and triisobutylaluminum. In the case of t=u=o and1.5≦r<3, are included dialkylaluminum alkoxide such as diethylaluminumethoxide and dibutylaluminum butoxide; alkylaluminum sesquialkoxide suchas ethylaluminum sesquiethoxide and butylaluminum sesquibutoxide; aswell as partially alkoxylated alkylaluminum having an averagecomposition represented by R⁶ ₂.5 Al(OR⁷)₀.5. Examples of the compoundcorresponding to the case where s=t=0 include a partially halogenatedalkylaluminum including dialkylaluminum halogenide (r=2) such asdiethylaluminum chloride, dibutylaluminum chloride and diethylaluminumbromide; alkylaluminum sesquihalogenide (r=1.5) such as ethylaluminumsesquichloride, butylaluminum sesquichloride and ethylaluminumsesquibromide; and alkylaluminum dihalogenide (r=1) such asethylaluminum dichloride, propylaluminum dichloride and butylaluminumdibromide. Examples of the compound corresponding to the case in whichs=u=0 includes a partially hydrogenated alkylaluminum includingdialkylaluminum hydride (r=2) such as diethylaluminum hydride anddibutylaluminum hydride; alkylaluminum dihydride (s=r) such asethylaluminum dihydride and propylaluminum dihydride. Examples of thecompound corresponding to the case in which t=0 include a partiallyalkoxylated and halogenated alkylaluminum such as ethylaluminumethoxychloride, butylaluminumbutoxy chloride and ethylaluminumethoxy bromide(r=s=u=1).

As the other organometallic compound, mention is made of anorganomagnesium compound such as butylethylmagnesium, an alkylzinccompound, an alkyllithium compound, etc. Examples of boron compoundinclude tripentafluoroborate, trifluoroborate and triethylborate.

The catalyst to be used in the process of the present inventioncomprises the above-mentioned components (A), (B), and (C) as theprincipal components. A variety of procedures are applicable to thepreparation of the catalyst, including (1) a method in which thecomponent (C) is added to the reaction product between the components(A) and (B) to prepare the polymerization catalyst, which is broughtinto contact with monomer/s to be polymerized; (2) a method in which thecomponent (A) is added to the reaction product between the components(B) and (C) to prepare the catalyst, which is brought into contact withmonomer/s to be polymerized; (3) a method in which the component (B) isadded to the reaction product between the components (A) and (C) toprepare the polymerization catalyst, which is brought into contact withmonomer/s to be polymerized; and (4) a method in which the components(A), (B), and (C) are added one by one to monomer/s to be polymerized tobring each of the components into contact with the monomer/s. There maybe employed the reaction product among the components (A), (B) and (C)which has been isolated and purified in advance.

The addition or contact of each of the components (A), (B), and (C) canbe carried out, of course, at the polymerization temperature and besidesat a temperature in the range of 0° to 100° C.

Examples of vinyl compounds to be preferably polymerized by the use ofthe catalyst according to the present invention include an olefin suchas ethylene, propylene, butene, hexene and octene, a diolefin,acetylenes, etc. in addition to styrene.

The process for producing a styrenic polymer is put into practice by theuse of the foregoing catalyst.

In producing the vinyl-based aromatic polymer according to the processof the present invention, a vinyl-based aromatic monomer such asstyrenic monomer exemplified by styrene and/or a derivative thereofexemplified by alkylstyrene, alkoxy styrene, halogenated styrene, vinylbenzoate ester or the like is polymerized or copolymerized in thepresence of the catalyst comprising the above-mentioned components (A),(B), and (C). As described hereinbefore, there are available variousmethods of bringing the catalyst of the present invention into contactwith the vinyl-based aromatic monomer.

The polymerization of the vinyl-based aromatic monomer such as styrenicmonomer may be carried out in bulk or in a solvent such as an aliphatichydrocarbon exemplified by pentane, hexane and heptane; an alicyclichydrocarbon exemplified by cyclohexane; or an aromatic hydrocarbonexemplified by benzene, toluene and xylene. The polymerizationtemperature is not specifically limited, but is 250° C. or lower,preferably 0° to 90° C., more preferably 20° to 70° C. A polymerizationtemperature exceeding 250° C. unfavorably causes violent thermalpolymerization of the monomer. The use of a gaseous monomer as astarting material is not specifically limited.

For the purpose of modifying the molecular weight of the vinyl-basedaromatic polymer to be produced, it is effective to proceed with thepolymerization reaction in the presence of hydrogen.

The styrenic polymer obtained by the process according to the presentinvention has a high degree of syndiotactic configuration.

Here, the vinyl-based aromatic polymer such as the styrenic polymerwhich has a high degree of the syndiotactic configuration means that itsstereochemical structure is mainly the syndiotactic configuration, i.e.the stereostructure in which phenyl groups or substituted phenyl groupsas side chains are located alternately at opposite directions relativeto the main chain consisting of carbon-carbon bonds. Tacticity isquantitatively determined by the nuclear magnetic resonance method (¹³C-NMR method) using carbon isotope. The tacticity as determined by the¹³ C-NMR method can be indicated in terms of proportions of structuralunits continuously connected to each other, i.e., a diad in which twostructural units are connected to each other, a triad in which threestructural units are connected to each other and a pentad in which fivestructural units are connected to each other. "The styrenic polymershaving such a high degree of syndiotactic configuration" as mentioned inthe present invention means polystyrene, poly(alkylstyrene),poly(halogenated styrene), poly(alkoxystyrene), poly(vinyl benzoate),the mixtures thereof, and copolymers containing the above polymers asmain components, having such a syndiotacticity that the proportion ofracemic diad is at least 75%, preferably at least 85%, or the proportionof racemic pentad is at least 30%, preferably at least 50%.Poly(alkylstyrene) include poly(methylstyrene), poly(ethylstyrene),poly(isopropylstyrene), poly(tert-butylstyrene) etc., poly(halogenatedstyrene) include poly(chlorostyrene), poly(bromostyrene),poly(fluorostyrene), etc, and poly(alkoxystyrene) includepoly(methoxystyrene, poly(ethoxystyrene), etc.

The most desirable styrenic polymers among them are polystyrene,poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tert-butylstyrene),poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), andthe copolymer of styrene and p-methylstyrene.

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

In the following, the present invention will be described morespecifically with reference to examples, which however, shall not beconstrued to limit the present invention thereto.

EXAMPLE 1

<Preparation of catalyst solution>

N,N-dimethylanilinium tetra(pentafluorophenyl)borate in an amount of0.128 g was suspended in 50 mL (milliliter) of toluene. Subsequently,the resultant suspension was incorporated with 1.8 mL of 2 mol/L (liter)solution of triisobutylaluminum in toluene and 18 mL of 10 mmol/Lsolution of (1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxidein toluene and further with toluene so as to make a total volume of 90mL of the resultant mixed suspension, which was stirred at roomtemperature for 60 minutes to prepare a catalyst solution, while theprocedure was carried out entirely in an atmosphere of nitrogen.

<Polymerization of styrene>

In a 30 mL glass ampule which had been dried and purged with nitrogenwere placed 10 mL of styrene and 20 μL (microliter) of 0.5 mol/Lsolution of triisobutylaluminum in toluene, and the ampule was sealedwith a Teflon cap and immersed in an oil bath at 60° C. After the lapseof 15 minutes, to the resultant mixture was added 188 μL of theabove-prepared catalyst solution to start polymerization, and thereactant was allowed to stand as it is for 4 hours. Then the polymerthus obtained was crushed, washed with methanol and dried at 150° C.under reduced pressure to recover 5.67 g of a polymer. It was confirmedthat the objective polymer was syndiotactic polystyrene having aweight-average molecular weight of 158,000, a syndiotacticity of atleast 95% as determined by ¹³ C-NMR spectrum method and a single meltingpoint at 270° C. The MEK (methyl ethyl ketone)-soluble portion underboiling was at most 3%. The catalytic activity in the polymerization wasequivalent to 310 kg/g-Ti.

EXAMPLE 2

The procedure in Example 1 was repeated to prepare the catalyst solutionand polymerize styrene by the use of the aforesaid catalyst solutionexcept that (1,2,3,4-tetramethylcyclopentadienyl)titanium trichloridewas used in place of (1,2,3,4-tetramethylcyclopentadienyl)titaniumtrimethoxide. As a result, a polymer was obtained in an amount of 0.53 gexpressed in terms of weight after drying and was proved to be asyndiotactic polystyrene having a weight-average molecular weight of135,000. The catalytic activity in the polymerization was equivalent to30 kg/g-Ti.

EXAMPLE 3

The procedure in Example 1 was repeated to prepare the catalyst solutionand polymerize styrene by the use of the aforesaid catalyst solutionexcept that (1,2,3,4-tetramethylcyclopentadienyl)trimethyltitanium wasused in place of (1,2,3,4-tetramethylcyclopentadienyl)titaniumtrimethoxide. As a result, a polymer was obtained in an amount of 4.27 gexpressed in terms of weight after drying and was proved to be asyndiotactic polystyrene having a weight-average molecular weight of183,000. The catalytic activity in the polymerization was equivalent to238 kg/g-Ti.

Comparative Example 1

The procedure in Example 1 was repeated to prepare the catalyst solutionand polymerize styrene by the use of the aforesaid catalyst solutionexcept that (1-ethyl-2,3,4,5-tetramethylcyclopentadienyl)titaniumtrimethoxide was used in place of(1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxide. As a result,a polymer was obtained in an amount of 4.32 g expressed in terms ofweight after drying and was proved to be a high-molecular-weightsyndiotactic polystyrene having a weight-average molecular weight of1,595,000. The catalytic activity in the polymerization was equivalentto 241 kg/g-Ti.

EXAMPLE 4

In a 5 L autoclave made of SUS were placed 2 L of styrene and 0.5 mL of2 mol/L solution of triisobutylaluminum in toluene, followed by heatingto 60° C. Subsequently, the resultant mixture was incorporated with 50mL of the catalyst solution as prepared in Example 1 and subjected toalternate heating and cooling repeatedly so as to maintain the insidetemperature at 50° C., to proceed with reaction for 4 hours. Thereafter,the reaction was arrested by adding 100 mL of methanol to the reactionsystem, and the content in the autoclave was washed with 5 L ofmethanol. The methanol-insoluble portion was separated by filtration anddried at 150° C. under reduced pressure for 5 hours to recover 1.34 kgof a polymer. It was confirmed that the objective polymer wassyndiotactic polystyrene having a weight-average molecular weight of210,000, a molecular weight distribution of 2.34, a syndiotacticity ofat least 95% as determined by ¹³ C-NMR spectrum method and a singlemelting point at 270° C. The MEK (methyl ethyl ketone)-soluble portionunder boiling was at most 2%. The catalytic activity in thepolymerization was equivalent to 280 kg/g-Ti, and the amount of theresidual ash was 4 ppm as Ti and 45 ppm as Al.

EXAMPLE 5

The procedure in Example 4 was repeated to carry out the polymerizationof styrene except that the catalyst solution and the 2 mol/L solution oftriisobutylaluminum in toluene which was incorporated in styrene wereused in amounts of 40 mL (instead of 50 mL) and 0.4 mL (instead of 0.5mL), respectively.

As a result, a polymer was obtained in an amount of 1.18 kg expressed interms of weight after drying and was proved to be a syndiotacticpolystyrene having a weight-average molecular weight of 200,000, amolecular weight distribution of 2.25, a syndiotacticity of at least 95%as determined by ¹³ C-NMR spectrum method and a single melting point at270° C. The MEK-soluble portion under boiling was at most 2%. Thecatalytic activity in the polymerization was equivalent to 307 kg/g-Ti.

The resultant polymer was incorporated with an antioxidant and meltmolded to produce a molding. A measurement was made of the yellownessindex of the resultant molding. The result was 7. Then the molding wasallowed to stand in an atmosphere of air at 150° C. for 24 hours tocarry out oxidation acceleration test with the result that yellownessindex was 19.

Comparative Example 2

The procedure in Example 1 was repeated to prepare the catalyst solutionand polymerize styrene by the use of the aforesaid catalyst solutionexcept that penta-substituted(1-ethyl-2,3,4,5-tetramethylcyclopentadienyl)titanium trimethoxide wasused in place of (1,2,3,4-tetramethylcyclopentadienyl)titaniumtrimethoxide and that the inside temperature was set at 80° C.

As a result, a polymer was obtained in an amount of 758 g expressed interms of weight after drying and was proved to be a syndiotacticpolystyrene having a weight-average molecular weight of 656,000, and amolecular weight distribution of 2.85. In spite of the elevatedpolymerization temperature, the resultant polymer had a high molecularweight and the MEK-soluble portion under boiling was as high as 5%. Thecatalytic activity in the polymerization was equivalent to 158 kg/g-Ti.

Comparative Example 3

The procedure in Example 1 was repeated to prepare the catalyst solutionand the procedure in example 2 was repeated to polymerize styrene by theuse of the aforesaid catalyst solution except thatpentamethylcyclopentadienyltitanium trimethoxide was used in place of(1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxide, that theinside temperature was set at 80° C., and that the catalyst solution andthe 2 mol/L solution of triisobutylaluminum in toluene which wasincorporated in styrene were used in amounts of 75 mL and 2.25 mL,respectively. As a result, a polymer was obtained in an amount of 1.43kg expressed in terms of weight after drying and was proved to be asyndiotactic polystyrene having a weight-average molecular weight of253,000, a molecular weight distribation of 2.55, a syndiotacticity ofat least 95% as determined by ¹³ C-NMR spectrum method and a singlemelting point at 269° C. The MEK-soluble portion under boiling was 5%.The catalytic activity in the polymerization was equivalent to 199kg/g-Ti.

The resultant polymer was incorporated with an antioxidant and meltmolded to produce a molding. A measurement was made of the yellownessindex of the resultant molding. The result was 10. Then, the molding wasallowed to stand in an atmosphere of air at 150° C. for 24 hours tocarry out oxidation acceleration test with the result that yellownessindex was as high as 35. The yellowing of the molding was clearly seenby visual observation.

EXAMPLE 6

In a 1 L autoclave made of SUS was placed 400 mL of heptane, which wasthen heated to 80° C. and was incorporated with 20 mL of the catalystsolution as prepared in Example 1. Subsequently, ethylene was fed in theautoclave and polymerized for 30 minutes at a constant ethylene pressureof 0.4 MPa, while the content was subjected to alternate heating andcooling repeatedly so as to maintain the inside temperature at 80° C.Thereafter, the reaction was arrested by adding 20 mL of methanol to thereaction system. The precipitate polymer, which was in granular form,was washed with 5 L of methanol. As a result, a polymer was obtained inan amount of 44.4 g expressed in terms of weight after drying, and wasproved to be polyethylene having a viscosity of 1.71 as determined indecaline at 130° C.

Comparative Example 4

The procedure in Example 6 was repeated to polymerize ethylene exceptthat the catalyst solution containingpentamethylcyclopentadienyltitanium trimethoxide as prepared inComparative Example 3 was used. As a result, polyethylene was obtainedin an amount of 8.4 g on dry base and had a viscosity of 12.3 asdetermined in decaline at 130° C., thereby showing an extremely highmolecular weight.

EXAMPLE 7

In a 30 mL glass ampule which had been dried and purged with nitrogenwere placed 10 mL of styrene and 30 μmol of triisobutylaluminum, and theampule was sealed with a Teflon cap, followed by temperature raising to70° C. In the ampule were further successively placed 0.5 μmol of(1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxide and 0.5 μmolof bis(cyclopentadienyl)ferrocenium tetra(pentafluorophenyl)borate toproceed with polymerization at 70° C. for 4 hours. After the completionof the reaction, the reaction product was washed with methanol and driedto afford 4.30 g of a polymer. The resultant polymer was subjected toSoxhlet extraction for 5 hours by the use of boiling methyl ethyl ketone(MEK) as the solvent to produce MIP (MEK-insoluble portion). As theresult, syndiotactic polystyrene was obtained at a yield of 3.18 g. Theresultant syndiotactic polystyrene had a weight-average molecular weightof 118,000. The catalytic activity in the polymerization was 133kg/g-Ti.

Comparative Example 5

The procedure in Example 7 was repeated to proceed with polymerizationexcept that triisobutylaluminum was not used. As a result, a polymer wasrecovered in a yield of 0.23 g, but was totally dissolved in MEK. Itturned out to be an atactic polystyrene without a definite meltingpoint.

EXAMPLE 8

A catalyst solution was prepared, in advance, by mixing in a nitrogenatmosphere, 10 mL of 0.1 mol/L solution of triisobutylaluminum, 5 mL of10 mmol/L solution of(1,2,3,4-tetramethylcyclopentadienyl)trimethyltitanium, 5 mL of 10mmol/L slurry of N,N-dimethylanilinium tetra(pentafluorophenyl)borate,each in toluene as a solvent and 5 mL of toluene. Subsequently, in a 30mL glass ampule which had been dried and purged with nitrogen was placed10 mL of styrene and the ampule was sealed with a Teflon cap, heated to70° C. and charged with 250 μL of the above-prepared mixed catalystsolution to proceed with polymerization at 70° C. for 4 hours.

After the completion of the reaction, the reaction product was washedwith methanol and dried to afford 4.72 g of a polymer. The resultantpolymer was subjected to Soxhlet extraction for 5 hours by the use ofboiling methyl ethyl ketone (MEK) as the solvent to produce MIP(MEK-insoluble portion). As the result, syndiotactic polystyrene wasobtained at a yield of 4.50 g. The resultant syndiotactic polystyrenehad a weight-average molecular weight of 99.000. The catalytic activityin the polymerization was 188 kg/g-Ti.

Comparative Example 6

The procedure in Example 8 was repeated to prepare catalyst solutionexcept that triisobutylaluminum was not used. AS a result, there wasproduced an oil which was insoluble in toluene. An attempt was made torecover a polymer by adding the product to styrene, but it turned out tobe failure.

EXAMPLE 9

The procedure in Example 7 was repeated to proceed with polymerizationexcept that there were used 50 μmol of methylaluminoxane in place of 0.5μmol of bis(cyclopentadienyl)ferrocenium tetra(pentafluorophenyl)borate,50 μmol of triisobutylaluminum in place of 30 μmol of the same and 0.25μmol of (1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxide inplace of 0.5 μmol of the same and the polymerization was carried out forone hour. As a result, a syndiotactic polystyrene having aweight-average molecular weight of 250,000 was obtained in a yield of1.65 g. The catalytic activity in the polymerization was 138 kg/g-Ti.

Comparative Example 7

The procedure in Example 9 was repeated to proceed with polymerizationexcept that triisobutylaluminum was not used. As a result, asyndiotactic polystyrene having a weight-average molecular weight of300,000 was obtained in an amount of 1.23 g. The catalytic activity inthe polymerization was as low as 102 kg/g-Ti.

As described in detail hereinbefore, the catalyst of the presentinvention has a high catalytic-activity. According to the process of thepresent invention which makes use of the catalyst of the invention, itis made possible to produce a styrenic polymer which has a high degreeof syndiotactic configuration and a low molecular weight, hardly causesyellowing and is minimized in the content of residual metals, at a lowproduction cost in high efficiency through simplified steps.

INDUSTRIAL APPLICABILITY

As described in detail hereinbefore, the catalyst according to thepresent invention can favorably be used as a catalyst for the productionof a vinyl-based polymer such as polystyrene and polyolefin, andaccording to the process of the present invention, it is made possibleto produce a vinyl-based aromatic polymer such as a styrenic polymerwhich has a high degree of syndiotactic configuration and a lowmolecular weight, at a low production cost in high efficiency throughsimplified steps.

We claim:
 1. A catalyst for the production of a vinyl aromatic polymer,which comprises: in combination, (A) a transition metal complex of theformula: ##STR5## wherein each of T¹, T², T³ and T⁴, independently ofeach other, is C₁₋₂₀ -alkyl or C₆₋₂₀ -aryl, M is a Group IV-VItransition metal and Q is C₁₋₂₀ or --SCH₃, (B) an aluminoxane or ioniccompound having a non-coordinating anion and a cation and (C) a Lewisacid.
 2. The catalyst of claim 1, wherein M is Ti, Hf or Zr.
 3. Thecatalyst of claim 1, wherein said (C) Lewis acid is a compound offormula: AlR¹ ₃, wherein R¹ is a C₁₋₈ -alkyl.
 4. The catalyst of claim1, wherein the aluminoxane has the formula: ##STR6## wherein n is ainteger from 2 to 50 and R² is C₁₋₈ -alkyl or said aluminoxane is acycloalkylaluminoxane of the formula (V): ##STR7## wherein R² is asdefined above.
 5. The catalyst of claim 1, wherein groups T¹ to T⁴ areeach methyl.
 6. The catalyst of claim 1, wherein said Lewis acid isselected from the group consisting of an organoaluminum compound offormula (VIII):

    R.sup.6.sub.r Al(OR.sup.7).sub.s H.sub.t X.sub.u

wherein R⁶ and R⁷ each independently represent a C₁₋₈ -alkyl group; X isa halogen; r, s, t and u each have a value within the ranges: 0<r≦3,0≦s<3, 0≦t<3, and 0≦u<3, and r+s+t+u=3; an organomagnesium compound, analkylzinc compound and an alkyllithium compound.
 7. The catalyst ofclaim 1, wherein said transition metal complex (A) is a member selectedfrom the group consisting of(1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium triethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium tripropoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium tributoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium triphenoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium (--SCH₃)₃,(1,2,3,4-tetramethylcyclopentadienyl)zirconium trimethoxide, and(1,2,3,4-tetramethylcyclopentadienyl)hafnium trimethoxide.
 8. A catalystfor the production of a vinyl aromatic polymer, which comprises: incombination, (A) a transition metal complex of the formula: ##STR8##wherein each of T¹, T², T³ and T⁴, independently of each other, is C₁₋₂₀-alkyl or C₆₋₂₀ -aryl, M is a Group IV-VI transition metal and Q isC₁₋₂₀ or --SCH₃, (B) an aluminoxane and an ionic compound having anon-coordinating anion and a cation and (C) a Lewis acid.
 9. Thecatalyst of claim 8, wherein M is Ti.
 10. The catalyst of claim 8,wherein said Lewis acid is selected from the group consisting of anorganoaluminum compound of formula (VIII):

    R.sup.6.sub.r Al(OR.sup.7).sub.s H.sub.t X.sub.u

wherein R⁶ and R⁷ each independently represent a C₁₋₈ -alkyl group; X isa halogen; r, s, t and u each have a value within the ranges: 0<r≦3,0≦s<3, 0≦t<3 and 0≦u<3, and r+s+t+u=3; an organomagnesium compound, analkylzinc compound and an alkyllithium compound.
 11. The catalyst ofclaim 8, wherein said transition metal complex (A) is a member selectedfrom the group consisting of(1,2,3,4-tetramethylcyclopentadienyl)titanium trimethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium triethoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium tripropoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium tributoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium triphenoxide,(1,2,3,4-tetramethylcyclopentadienyl)titanium (--SCH₃)₃,(1,2,3,4-tetramethylcyclopentadienyl)zirconium trimethoxide, and(1,2,3,4-tetramethylcyclopentadienyl)hafnium trimethoxide.
 12. A processfor the production of a vinyl aromatic polymer, whichcomprises:polymerizing a vinyl aromatic monomer in the presence of acatalyst which is a combination of (A) a transition metal complex of theformula: ##STR9## wherein each of T¹, T², T³ and T⁴, independently ofeach other, is C₁₋₂₀ -alkyl or C₆₋₂₀ -aryl, M is a Group IV-VItransition metal and Q is C₁₋₂₀ -alkoxy, (B) an aluminoxane or ioniccompound having a non-coordinating anion and a cation and (C) a Lewisacid.
 13. The process of claim 12, wherein said Lewis acid is a memberselected from the group consisting of an organoaluminum compound offormula (VIII):

    R.sup.6.sub.r Al(OR.sup.7).sub.s H.sub.t X.sub.u

wherein R⁶ and R⁷ each independently represent a C₁₋₈ -alkyl group; X isa halogen; r, s, t and u each have a value within the ranges: 0<r≦3,0≦s<3, 0≦t<3, and 0≦u<3, and r+s+t+u=3; an organomagnesium compound, analkylzinc compound and an alkyllithium compound.
 14. A process for theproduction of a vinyl polymer, which comprises:polymerizing a vinylaromatic monomer in the presence of a catalyst which is a combination of(A) a transition metal complex of the formula: ##STR10## wherein each ofT¹, T², T³ and T⁴, independently of each other, is C₁₋₂₀ -alkyl or C₆₋₂₀-aryl, M is a Group IV-VI transition metal and Q is C₁₋₂₀ -alkoxy, (B)an aluminoxane and an ionic compound having a non-coordinating anion anda cation and (C) a Lewis acid.
 15. The process of claim 14, wherein saidLewis acid is a member selected from the group consisting of anorganoaluminum compound of formula (VIII):

    R.sup.6.sub.r Al(OR.sup.7).sub.s H.sub.t X.sub.u

wherein R⁶ and R⁷ each independently represent a C₁₋₈ -alkyl group; X isa halogen; r, s, t and u each have a value within the ranges: 0<r≦3,0≦s<3, 0≦t<3, and 0≦u<3, and r+s+t+u=3; an organomagnesium compound, analkylzinc compound and an alkyllithium compound.